1. Field of the invention
The present invention relates to power transmission belts and in particular to raw-edged V-belts suitable for use in clutching applications.
2. Description of the Related Art
V-belts are commonly used to transmit power as between pulleys. V-belts, characterized by a substantially trapezoidal cross section and generally comprising elastomeric tension- and compression sections and a load-carrying section disposed between the tension- and compression sections, are also commonly utilized in clutching-type drive applications, wherein the V-belt is alternately made to establish and disengage from a power transmitting function between two pulleys, such as by a cam, an idler pulley, through the use of a clutch sheave or a movable clutching center, or by any other conventional mechanism well known to the art.
Of concern in clutching-type drive systems is the incremental time of clutching, i.e., of engagement and of dis-engagement of the belt from the balance of the drive system, i.e., from its power transmitting function. Peripheral component protection, operator safety and convenience often call for the incremental time of clutching to be extended so that high inertial torque forces are not transmitted to the component operated by the drive system, or to the operator of such component; e.g., of the rider lawn mower or the tiller.
In conventional raw-edged- or non-banded V-belts, one or more layers of rubberized fabric is provided on at least one of the outer surface of the tension section and the outer surface of the compression section, but the side edges of the belt are raw, i.e., remain uncovered. These rubberized fabric elements decrease the amount of belt rubber contacting the sheave sidewalls during use, by substituting layers of rubber with layers of fabric, thus reducing the overall coefficient of friction of the side-wall-engaging belt surface and reducing the belt""s aggressiveness. Because the sidewalls are uncovered and large portions of the compression section elastomer remain exposed however, raw edged V-belts are usually sidewall-aggressive in clutching applications, and result in rapid engagement during the de-clutching procedure. Such rapid engagement maximizes the aforementioned high inertial torque forces.
Moreover, raw-edged V-belt sides are exposed to high degree of abrasion in clutching drive systems, and the gum compounds typically used to skim the fabric elements thus experience a high degree of wear in the area in which the rubberized fabric element or member contacts the pulley, i.e., at the fabric edges. This leads to uneven V-belt side surface wear, voids between lamination fabric layers, and non-uniform V-belt to pulley sidewall fit, which leads to a deterioration of proper engagement characteristics. In addition, conventional raw-edged V-belts generally exhibit poor reverse bending properties.
The present invention provides a raw-edged V-belt for clutching-type drive applications, comprising a belt body having a compression section and a tension section and a load-carrying section disposed between the tension- and compression sections and comprising at least one longitudinally extending tensile element. The compression section possesses an outer portion and an inner portion, at least the outer portion comprising three or more layers of a rubberized textile member.
The rubberized textile members comprise a textile component and a rubber component, and in at least one of the rubberized textile member layers, the textile component is formed and arranged such that at least the greater proportion of the total textile component is orientated in any one direction exclusive of both the direction of travel of the belt and its transverse. This arrangement in at least one of the V-belt""s rubberized textile member layers results in a structural imbalance in the V-belt, which causes the belt to exhibit favorable engagement and disengagement characteristics in clutching applications.
In a preferred embodiment of the present invention, at least one of the rubberized textile member layers comprises a knitted or woven fabric element coated on at least one side with a rubber and fiber composite. According to this preferred embodiment of the invention, the fibers in the rubber and fiber composite improve the abrasion resistance of the belt, thus decreasing the occurrence of poor pulley-to-sidewall fit with extended use of the belt in clutching-type applications. According to a further preferred embodiment, at least a greater proportion of the fibers in the rubber and fiber composite are orientated in a direction other than the belt""s direction of travel or its transverse.
Another feature of the present invention is to provide a belt of the type herein described which may be used satisfactorily in applications characterized by reverse bending conditions.
A clutching-type drive assembly is moreover provided, comprising a belt of the present invention trained about at least one driver pulley and at least one driven pulley, and further comprising a clutching member.
A method of improving the engagement and disengagement characteristics of a V-belt in clutching applications is moreover provided, characterized by the orientation or alignment of at least the greater proportion of the textile component in at least one of the rubberized textile member layers of a V-belt compression section outer portion, in a first direction, which is distinct from both the direction of travel of the V-belt and the transverse thereof.